1. Field of the Invention
The present invention relates to a light emitting device, and more particularly, to a method for manufacturing light emitting devices. The method may reduce the inner pressure of a laminated image emitting device panel to prevent failure of the panel.
2. Discussion of the Related Art
Thin light emitting devices for use as information display devices have recently gained popularity. These light emitting devices may be as thin as a sheet of paper. The light emitting device itself may be a self-emission device that uses a thin light emitting layer between electrodes. The device has many advantages, such as low power consumption, thinness, and self-emission.
Light emitting devices include pixels arranged in a matrix to display an image. Each sub-pixel may include a light emitting cell and a drive portion that independently drives the light emitting cell.
The light emitting cell may include a pixel electrode connected to the drive portion, a common cathode connected to ground, and a light emitting element formed between the pixel electrode and the common cathode.
The drive portion may include a storage capacitor and two transistors connected between a power supply line, a data line, and a gate line. The drive portion drives the pixel electrode of the light emitting cell. The power supply line may provide common drive power, the data line may provide a video data signal, and the gate line may provide a scan signal.
Drive portions and light emitting portions may be formed to oppose each other on two substrates. The two substrates may be laminated together with a seal, thereby providing an encapsulation structure. This structure may be provided in a vacuum chamber. The drive portions drive the light emitting portions to emit light through the substrates.
If the substrates of the light emitting device are laminated using an inert gas at room temperature, the initial inner pressure between the upper substrate and lower substrate of the light emitting device including light emitting portions on the upper substrate and drive portions on the lower substrate as described above is about 30-40 torr.
However, the inner pressure of a related art light emitting device will increase to above 100 torr during reliability tests involving high temperature and high humidity. FIG. 1 illustrates a related art light emitting device which includes an upper substrate 1, a lower substrate 2, light emitting portions 4, drive portions 5, contact electrodes 6, and a seal 7. In edge portions of the upper substrate 1 and the lower substrate 2 where the seal 7 is formed, drive portions 5 are connected to light emitting portions 4 through contact electrodes 6. However, in middle portions of the upper substrate 1 and the lower substrate 2, contact electrodes 6 are not in contact with drive portions 5 due to the increased inner pressure. Thus, the light emitting device may fail to function.